Method and apparatus for determining equilibrium vaporization end point



June 14 1927.

- C. E. PARSONS ET AL METHOD AND APPARATUS FOR DETERMINING EQUILIBRIUM VAPORIZATION END POINT Filed 001;. 6, 1926 2 Sheets-Sheet l m 14 1927. J c. E. PARSONS ET AL METHOD AND APPARATUS FOR DETERMINING EQUILIBRIUM VAPORIZATION END POINT Filed Oct. 6, 1926 2 Sheets-Sheet 2 INVENTOR Patented June 14, 1927.

UNITED STATES 1,632,748 PATENT OFF-ICE.

CHARLES E. PARSONS, 0F ENGLEWQOD, NEW JERSEY, AND RESTON STEVENSON, OF NEW YORK, N. Y., ASSIGNORS TO WILLIAM I. DEPZPE, NEW YORK, N. 'Y.

vMETHOD AND APPARATUS FOR DETERMINING EQUILIBRIUM VAPORIZATION END POINT.

Application. filed October 6, 1926. Serial No. 139,951.

This invention relates more particularly to an improved method for determining the boiling or vaporization point of liqu ds when completely vaporized under equilibrium conditions. The temperature or point at which complete equilibrium vaporization is effected is commonly called the equilibrium vaporization end point, and is identical with the dew point at the pressure or par.- tial pressure obtaining at the time of the determination. The invention also relates to apparatus for carrying out the method, and particularly to apparatus adaptedfor laboratory use in the practical determination of the vaporization or dew point of commercial gasoline, kerosene, and other liquid fuels adapted for or used in internal combustion engines.

Natural petroleum is not a single liquid witha definite boiling point, but comprises a number of hydrocarbon compounds mutually dissolving each other or consolute and, therefore, well known petroleum products such as gasoline and kerosene are not of simple or of definite composition, but are made of a plurality of hydrocarbon compounds having different boiling or vaporization points. Obviously, in operating an internal combustion engine, it is desirable to completely vaporize all of the liquid hydrocarbons without fractional distillation and without residue. It has been found that this can be done most successfully by equilibrium vaporization, whereby all of the vapors are n'iaintained in intimate contact with all the liquids until vaporization is completed.

By vaporization under equilibrium conditions, the various hydrocarbon constituents of the motor fuel, which mutually dissolve each other, and their vapors, are kept in intimate contact until a temperature is reached where vaporization of the entire mass or mixture of liquids is completed. Under equilibrium conditions. it will be seen that vapors of all the liquids are intimately mixed. each vapor exerting itsoown partial pressure and being superheated relatively to its own vaporization temperature, but, on

accountof the intimate relation maintained during equilibrium vaporization, the end point-,boiling point or temperature of complete vaporization of the mixed liquids, under equilibrium conditions, is consider determined by volatility tests under the En'gler flask method. According to the Engler flask method, the liquid to be tested is placed in a flask and heated, the temperature rising as fractions are vaporized and removed. The rise in temperature for each successive 5% of the volume vaporized is determined until the end point is reached when no mole of the liquid is distilled, leaving in the Engler flask a residue of tarry and gummy substances, representing about 5% of the original liquids.

Obviously, therefore, by the Englcr'fiask method, volatilization takes-place according to fractional distillation, for the successive vapors are removed as fast as they are generated, leaving at each step a residual liquid in the flask, the specific gravity of which is gradually increasing. The application of increasing temperatures is thus required to eflect vaporization. The end point or boiling point of the last 5% or 10% of the liquid in the Engler flask therefore, does not represent the vaporization point of the entire liquid, nor does it correspond to the end point or boiling point when the same liquid is vaporized under equilibrium conditions, that is, with all the vapors retained in intimate contact with all the liquids untilthe latter are completely vaporized. In fact,

experiment has shown that a commercial gasoline, incompletely vaporized at the Eng ler end point of 206 0., was completely vaporized under equilibrium conditions at 145 C.

Heretofore it has been common practice to operate internal combustion engines according to'the wet mixture method and this method is in use today to a considerable extent, where the superheated dry gas method has not been adopted. However, many improved cars of today have engines operating on a completely homogeneous dry gaseous mixture. which Is generated in the intake system under equilibrium conditions, For this reason and because the Engler flask standard for the determination of the volatility of gasolines or other hydrocarbon mixtures, is antiquated, inaccurate and unsatisfactory, there is a demand for a more reliable method. The Engler distillation ives a curve which permits only a vague interpretation which does not correspond to complete vaporization under conditions of the dry mixture automobile practice.

The Bureau of Standards and Budget Bureau which have established the grading of motor fuel oils according to the Engler flask method, have endeavored recently, to find a simple method for readily determining the vaporization or dew point of liquid fuels vaporized under equilibrium conditions. The apparatus previously employed is more or less complicated and requires careful handling and testing through SUCL :ssive stages and, therefore, is notsuitable for general laboratory practice, such as would be required if the quality of fuel oils were based on end points or vaporization points, determined by equilibrium vaporization.

In view of the fact that motor fuel oils of commerce comprise a plurality of hydrocarbons of varying specific gravities and boiling points, it is difiicult, if not impossible, to accurately determine the quality of the fuel oil by the Engler flask method, particularly when the motor fuel is to he used in an internal combustion engine, operating under equilibrium vaporization conditions. Motor car practice is .coming more and more to the adoption of engines equipped for delivering a superheated dry gaseous mixture produced under equilibrium conditions and, therefore, oil refiners as well as automobile factory laboratories are demanding a more precise and scientific method of determining the vaporization point of a mixture of hydrocarbon liquids, such as are found in ordinary commercial gasoline.

The superheated dry gas method which involves vaporization under equilibrium conditions in the manifold system and the maintenance and delivery to the engine of a homogeneous dry gaseous mixture, was first discussed and perfected by lVilliam P. Deppe, and his method of operating an internal combustion engine is more particularly described in his patents, No. 1,335,665 of March 30. 1920, and No. 1,360,098 of November 23, 1920. It has been in connection with this method that the inadequacy of the Engler flask method of determining gasoline qualities has developed and the determination of the Deppe equilibrium vaporization end point has been established.

Research work based on the disclosures and teachings of the Deppe patents, was conducted and the results have been published by Stevenson and Stark, Industrial and Engineering Chemistry, XVII 679 (1925). This article was entitled Equili brium vaporization of gasoline and it gives the results of experiments upon the procedure of equilibrium vaporization, the method of determining the equilibrium end point which is called the Deppe end point in their paper) and the relation between this end point and the dew point or equilibrium end point of iii-gasoline mixtures suitable for automo- However, the method and apparatus used by Stevenson and Stark in the above research for. the determination of the equilibrium end point of gasoline and similar fuels, was not simple and not adapted for general laboratory use.

The object, therefore, of our improvement is to provide a simple laboratory method and apparatus for the accurate determination of the equilibrium vaporization end point for motor fuels, the method being carried out by means of a comparatively simple apparatus wherein the liquid to be tested is vaporized under equilibrium conditions and suitable means are provided for condensing a negligible portion of the vapors to thereby determine the dew point or end point.

In carrying out this object, the preferred form of our apparatus is provided with a vertically disposed conduit, having a plural- .f

ity of transversely extending screens or perforated members, and the conduit is surrounded by a heating jacket through which steam or other suitable heating medium may be. passed to raise the temperature of the screens sufficiently to vaporize (under equilibrium conditions) the liquid passing through the conduit. The liquid to he vaporized is dropped slowly onto the first screen where it will spread out in thin films over the metal structure of the screen, any surplus liquid dropping onto the second and succeeding screens. In this manner intimate contact is maintained between the liquid and its vapors until vaporization is com-- pleted After complete vaporization, the vapors are superheated.

A further object, therefore, is to provide for superheating the va )ors of the liquids evaporated under equilibrium Conditions, this being effected by the screens and lower end of the heated conduit. Means are provided for maintaining and conducting the superheated vapors over a tip or surface plated with platinum black, which may be cooled artificially so that very small portions of the superheated vapors may be condensed thereon, thereby indicating the dew point or vaporizing point.

It is Well known that liquid vapors may he superheated as soon as the vapors are out of contact with their liquid and the temperature thereof is raised above the boiling or vaporization point, and further, that when such vapors are brought into contact with a Ill?) cooled surface, they will condense or form a blush of dew thereon at a temperature identical with the boiling or vaporization point. Accordingly, this principle is taken advantage of in our method by passing the vapors over a metal tip plated with platinum black, the surface of which, it has been found, will reflect a beam of light when there is the least precipitation or condensation of liquid particles thereon. Obviously, if the temperature of such a platinum black tip can be accurately controlled and determined an efficient and satisfactory means is available for accurately determining the equilibrium vaporization end point, that is, the boiling oint or dew point, all being the same.

The metal tip is preferably made of platinum or of gold or of platinum plated with gold, but the tip can be-made of a base metal. This tip is plated with platinum black according to a well known process described 7 in Findlay, Practical Physical Chemistry, under the chapter on Conductivity, and for which several modifications are referred to in Clark: The determination of hydrogen ions. This tip may be shorter than one inch and should be hollow like a thimble. We have made our own tips from platinum blow pipe tips.

The platinum black tip is supported on a tube, such as a glass tube, to which it is cemented with sodium silicate plus infusorial earth or other suitable adhesive.

This glass supporting tube extends outside of the apparatus and permits a small tube to enter and to reach up into the tip so that the tip can be cooled down as by a current of air, and to an extent and at a rate which may be controlled.

A further object of our improvement is to provide a conduit passing throu h a Dewar bulb, or other suitable means, or maintaining the vapors in the superheated state while passing them over the platinumblack tip, at the same time providing an. air current or other suitable means for lowering the temperature of the platinum-black -perature of the tip. Preferably tip until condensation appears thereon and then ascertaining or determinin the temfor the latter purpose, a thermoelectric couple is secured to the platinum-black tip, the leads of which are connected with a' suitable indicating pyrometer. By the cooling means, 'the platinum-black tip can be cooled until a temperature read. Then, if the cooling medium is withdrawn or diminished or discontinued, thereby permitting the dew or con densate on the platinum-black tip to evaporate as" the temperature of the tip rises, it will be found that the pyrometer will indicate the same temperature, that is, the temperature as read during the cooling operalaboratorv stand through the lower the liquid vapors tion, the instant the first blush of condensation appears.

A preferred form of laboratory apparatus for carrying out our improved method of determining equilibrium vaporization end points is illustrated in the accompanying drawings, in which Fi 1 is a side elevation of the apparatus with portions thereof in vertical section s; Fig. 2 is' an enlarged vertical sectional View of the Dewarbulb and the platinum-black tin cooling arrangement; Fig. 3 is a transverse section of the vaporizing conduit and jacket, the section being taken on the line 33 of Fig. 1; Fig. 4: isa transverse section of the lower end of the conduit below the Dewar bulb, the section being taken on the line 4-4. of Fig. 2; and Fig. 5 is a sectional detail of a modified arrangement for introducing air, or mixtures to be tested.

Referring to the drawings and more particularly to Fig. 1,

is provided with a base 1 and an upright supporting rod 2, upon which the various portions of the apparatus may be supported by suitable clamps or brackets. At the upper end of the apparatus, and supported by a bracket or clamp 3 secured to the rod 2, there is mounted a suitable supply reservoir 4, which may comprise a bulb, pipett or other suitable contalner, which is preferably graduated, as illustrated at5 in Fig. 1, so that the quantity of fluid tested may be measured or accurately determined.

The lower end of the storage reservoir 4 is preferably reduced in diameter toprovide a tube 6, which is fitted with a suitable valve or stop cock 7, adapted to be utilized for regulating or cutting off the flow of liquid end of the tube 6. The lowerend of the tube 6, in the present instance, is inserted in the end of a larger, transparent tube 8 (Fig. 1) and held attached thereto by means of a perforated cork or connector 9. The tube 8 (which is herescreens, as indicated in Fig. 3. The screens are preferably of copper and soldered, brazed or otherwise supported in good heat conductin contact with the conduit 11, so that when the conduit is heated, the screens or foraminous members will likewise be heated.

In order to properly heat thescreens 12 and conduit 11, the latter issurrounded by a jacket 13, which may be of'copper or the it will be noted that a like, and this jacket is preferably surrounded by a covering 14 of heat insulating material, substantially as indicated in Figs. 1 and 3.

For heating the conduit 11 and screens 12, to vaporize gasoline and other hydrocarbon fuels, such as ordinarily used in internal combustion engines, it is found that heating the conduit 11 may be satisfactorily effected by passing superheated steam through the jacket 13. For this purpose, the lower end of the jacket is preferably provided with an inlet tube 15, to which a superheating steam coil 16 is connected, the latter being preferably surrounded by a jacket 17 and adapted to be heated by suitably placed Bunsi -n burners 18. The latter are represented in Fig. 1 as supportedupon a bracket 19 mounted upon the base plate 1 of the apparatus.

Steam from any suitable source of supply may be conducted to the superheating coil 16 through the pipe 20.'

In order to determine the temperature of the superheated steam entering the jacket 13, the inlet pipe 15 is preferably provided with a flanged opening 21, fitted with a perforated cork 22, carrying a. thermometer 23. An exhaust pipe 24 leads from the upper end of the jacket 13 and this pipe is likewise provided with a flanged opening 25, carrying a thermometer 26 for determining the temperature of the steam leavin the jacket.

Preferably the outer end 27 of the exhaust pipe 24 is connected by a union 28, with a pipe 29, leading to a condensing coil 30, mounted in a suitable condenser 31, so that the steam may be condensed and collected from the lower end of the pipe 32 if desired.

The lower end of the equilibrium vapori zation conduit 11 is, in the present instance, connected with a conical extension 32, which is secured centrally of a hemispherical end piece 33 inserted in the lower end of the jacket 13, as will be seen in Fig 1 of the drawings. A perforated stopper or plug 34 is preferably inserted in the conical extension member 32 to .form a tight connection between the conduit 11 and a continuing conduit 35 passing through and integral with a Dewar bulb 36, formed of glass or other suitable transparent material, as more particularly shown in Fig. 2. In order to support the Dewar bulb 36 in the position indicated in Fig. 1, threaded bolts or rods 37 are preferably secured to the lower end of the jacket 13. the bolts supporting a ring or block 38 engaging the lower end of the Dewar bulb and adapted to hold the latter in place by suitable nuts 39. A ring or packing 4O ispreferabl mou nted between the upper shoulder of t e Dewar bulb and the hemispherical end member 33. By this arrangement, it will be seen that the nuts 39 on the ends of the bolts 37 permit removal or adjustment of the Dewar bulb as may be desired.

Near the lower end of the Dewar bulb conduit 35, there is provided a branch outlet 41 for'conducting the vapors to a condenser, substantially as shown in Fig. 1. This vapor outlet 41 is preferably connected by a suitable connector 42 with the end 43 of a condenser coil 44, mounted in a suitable condenser tank, which, in the present instance, is the tank 31, previously referred to as containing the condenser coil-30 for condensing the steam. The condensate of liquid fuel or other test liquid may be collected from the pipe 45.

The lower end 46 of the Dewar bulb conduit 35 is preferably closed by a perforated stopper or plug 47, through which there extends a tube 48 open at its lower end and closed at its upper end. The up er or closed end of the tube 48 lies near the center of the Dewar bulb and is closed by a conical metal tip 49, having its outer surface at 50, coated with platinum-black. Within the tube 48, there is mounted a smaller tube 51, adapted to conduct air or other cooling medium into the platinum-black tip, substantially as indicated by the arrows in Fig. 2. The lower end 52 of the small tube 51 may be connected to a compressed air tank or other suitable source of cooling fluid.

It will be seen that by passing air, for instance, through the tube 51, the temperature of the platinum-black tip may be reduced as desired, the air returning downward through the annular channel 53, lying between the tubes 48 and 51. To ascertain the temperature of the platinum-black tip 50, there is preferably attached to the tip end thereof. a thermo-couple 54 provided with leads 55 and 56, carried downward through the end closing plug 47, as will be seen from Fig. 2. The leads 55 and 56 may be connected in the usual manner with an indicating pyrometer (not shown) from which the temperature may be read directly.

The vapors after being superheated by passing downward through the screens 12 in the lower part of the conduit 11 will enter the conduit 35 and pass downward therein over the platinum-black tip 50 and out through the tube or pipe 41--43 to the condenser. It is possible that some liquid may be condensed in the conduit 35, and, for the purpose of removing any such condensate, the end plug 47 is preferably provided with a drainage tube 57. passing therethrough and adapted to drain off any liquid collecting in the lower end of the conduit 35.

In order to assist those desiring to construct apparatus for their own use, or for the laboratory determination of equilibrium vaporization end points, it is thought desirable to indicate the dimensions of the ap paratus described. For instance, the dian1 eter oi the screen conduit 11, in the apparatus shown. is /4 of an inch and the screens 12, are placed of an inch apart. The length of the screen conduit 11 is not so important, but in the present instance, the length is 7 inches. In the apparatus shown, the conduit of the Dewar bulb is approximately 6 inches long and 7 of an Inch inside diameter. 1t is believed that with these more important dimensions given,

the dimensions of other parts of the apparatus. can be readily determined by relative proportions, from the drawings which are substantially to scale.

For carrying out ourmethod, the opera-- tion is substantially as follows:-Steam is admitted through the tube or pipe 20, after which the Bunsen burners 18 are lighted, so as. to superheat the steam passing through the coil 16. The superheated steam from t e toil 16 will pass through the inlet opening 15 into the jacket 13 and the temperature of the steam entering the jacket may be determined by the' thermometer 23. The steam used for heating the conduit 11 will pass out from the jacket 13 through the tube or pipe 24 -29 and its temperature may be determined by-the thermometer 26. When it is indicated that the conduit and screens 12 have attained the desired temperature, the

stop-cock 7 is opened slightly to permit the liquid fuel from the reservoir 4 to pass down through the tube 6 and drop from the lower end thereof through the tube 8, which is preferably of glass or provided with a sight window, so that the rate of flow by drops may be observed and regulated. The gasoline or other liquid fuels being tested, will drop onto the first of the screens 12 and spread out thereover in thin films; any sur-- plus from the first screen dropping onto the second screen and so on down through the conduit 11. Filming or surfacing the liquid fuel in this manner on the screen or perforated members, which lie transversely of the direction of flow, facilitates rapid vaporization, (under equilibrium conditions) because the screens, as previously pointed out, are heated by the superheated steam passing through the surrounding jacket 13. It will be found that most hydrocarbon fuels, such as gasoline, kerosene and the like, which are made up of a plurality of hydrocarbons of different molecular weight, will be completely vaporized after passing through three or four'of the screens 12,, after which the screens and the heated conduit serve to superheat the vapors, the amount of superheating depending upon the temperature of the superheated steam.

The superheated vapors upon leaving the lower end of the conduit 11 pass into the Dewar bulb conduit 35 and are carried downward over the surface of the platinum-black tip 50, located on the upper end of the tube 48 (see Fig. 2) and then outward throu h the tube or pipe connections 4143 to t e condenser. Condensing the vapors in the coil 44, obviously will provide a forced downward draft and movement of the vapors through the conduits 11 and 35. If, however, there should be any condensation in the conduit 35, it will settle to the bottom and may tip 50 until the surface thereof shows a blush of condensate, which is immediately indicated by the reflection of light from the tip. Ordinarily, the platinum-black tip 50 appears dead black in a beam of light, but it is found that if the beam of light is kept upon it throughout the test, light will be reflected from the tip the instant any condensation of liquid takes place upon the platinum-black surface. For the purpose of cooling or lowering the temperature of the platinum-black tip, a stream of air is preferably projected against the underside of the tip by means of the tube 51, the air exhausting downward around the tube 51 through the annular channel 53, as indicated by arrows in Fig. 2. The cooling current of air should be carefully regulated, so that the cooling effect, on the platinum-black tip, is under control of the operator, and may be stopped at any time desired. In the mean time, by means of the 1 thermo-couple 54 and the indicating pyrometer connected therewith, the temperature of the platinum-black tip may be readily ascertained and the temperature at which the first blush of condensate appears upon the platinum-black tip read, thus determining the dew point, vaporization or boiling point, under equilibrium conditions, of the motor fuel or other liquid being tested. Bycutting off the flow of cooling air through the pipe 51, after the dew point is determined, cooling of the platinum-black tip will cease and immediately the blush of condensate will disappear. Upon reading the pyrometer when the blush of condensate disappears from the tip, it will be found that the temperature is substantially identical with the dew point temperature read when the first blush of condensate appears. In this manner the vaporization point and dew point are found to be identical and the temperature can be read as just stated, either as the temperature of the platinum-black tip is lowered or as its temperature is rising.

The apparatus as thus far described and the operation given relate to pure vapors of the liquids tested under atmospheric pressure, but it may be desirable to determine equilibrium vaporization end points in air mixtures, either by mixing air directly with the liquids and vapors passing into and through the conduit 11 or by passing a previously prepared mixture therethrough. In order that the apparatus may be utilized in this manner, Fig. 5 shows a modification, in which the sight glass 8 is replaced by a T- connector 58, the tubular stem 59 of which is provided with a. stop-cock 60 for regulating the flow of air or mixture which may be admitted through the pipe connection at 61. When the apparatus is arranged in this manner, liquid fuel from the reservoir 4 may be admitted to the conduit: 11 by turning the stop-cock 7, as previously indicated, and air admitted through the branch pipe 59 by opening the stop-cock 60. On the other hand, if it is desired to test a mixture of air and motor fuel or other liquid vapors in predetermined ratio, the stop-cock 7 may be completely closed and the desired previously prepared mixture admitted through the branch pipe 59. When. testing liqui fuel and air mixtures, it will be understood that the liquid fuels and vapors are under partial pressure conditions and the vaporization temperatures under equilibrium con ditions will be materially reduced, but such temperatures may be readily determined by passing the su erheatcd vapor mixtures over the platinumlack ti 50 and reducing the temperature of the latter in the manner previously described.

While we have described our method and a preferred form of apparatus for performing the same, we do not wish to be limited to the specific details shown and described, for obviously, various modifications therein can be made without departing from the spirit and scope of the invention.

We claim 2-- 1. The method of determining the equilibrium vaporization end-point of liquids, which comprises completely vaporizing the liquid, superheating the vapors thus formed, then cooling a minute portion of said vapors and to condensation ascertaining the temperature of condensation.

2. The method of determining the equilibrium vaporization end-point of liquids, which comprises completely vaporizing the liquid under equilibrium conditions, superheating the vapors thus formed, then passing the superheated vapors over a surface while reducing the temperature thereof and then determining the temperature of said surface when condensation of the vapors appears thereon.

1 temperature sutlicient to vaporize the liquid 3. The method of determining the equilibrium vaporization end-point of liquids, which comprises vaporizing a plurality of successive surfaces of the liquid in the presence of the vapors generated, superheating said vapors and passing them over a SUI- face adapted to be artificially cooled, cooling said surface until condensation of the vapors appears thereon, thcn ascertaining the temperature at which such condensation takes place.

4. The method of determining the cquilihrium vaporization end-point of liquids, which comprises filming the liquid in successive stages transversely of the direction of flow of the vapors, vaporizing the filmed liquid in intimate contact with its vapors for equilibrium vaporization, superheating the vapors when vaporization is com )letcd and passing them over a surface aciaptcd to indicate condensation, cooling said surface until condensation is indicated, then taking the temperature of the surface, said temperature representing the vaporization or dew point of the li uid.

5. The method 0 determining the equilibrium vaporization end-point of liquids, which comprises heating a plurality of successively disposed perforated members to a under equilibrium conditions and superheat the vapors, then permitting the liquid to drop on the first and successive perforated members while the vapors are conducted therethrough until complete vaporization is effected under equilibrium conditions, and the vapors superheated, passing the superheated vapors over a surface adapted to he artificially cooled, cooling said surface until precipitation of vapors is indicated thereon, then taking the temperature of said surface, said temperature representing the vaporization or dew point for the liquid.

6. Apparatus for determining the equilibrium vaporization end-point of liquids, which comprises a conduit, a plurality of screens or perforated members located in spaced relation transversely of said conduit, means for heating said conduit and the screens or perforated'members, means for droppin liquid fuel to be vaporized on the first an successive screens or perforated members, while conducting the vapor therethrough, the temperature of the perforated members being regulated to effect complete vaporization under equilibrium conditions, and subsequent superheating of the vapors, an element having a surface over which said vapors are adapted to pass for indicating the condensing point of the vapors, means for varying the temperature of said surface and means for ascertaining the temperature of said surface.

7. Apparatus as claimed in claim 6, in which means is provided for sight determiing the liquid tion of the nation of and regulating the flow of liquid into said conduit.

8. Apparatus as claimed in claim 6, in which said variable temperature surface is enclosed. in a heat insulated conduit and a thermo-couple attached to said surface is adapted for ascertaining its temperature.

9. Apparatus as claimed in claim 6, m which the means for varying the temperature of said surface comprises conduits for 'circulating-air for cooling said surface.

10. Apparatus for determining the equilibrium vaporization end-point of liquids, comprising a conduit, a plurality of screens or perforated members mounted in spaced relation transversely of said conduit, means for heating said conduit and the screens or perforated members, and maintaining them at a temperature for completely vaporizing the liquid under equilibrium conditions and superheating the vapors, means for introducfuel to be vaporized into said heated conduit, means for passing the superheated vapors over a surface adapted to indi- (ate condensation thereon, and means for varying the temperature of said surface.

11. Apparatus as claimed in claim 10, in which said condensing surface is mounted in a conduit formed in a Dewar bulb and meansv is provided for utilizing circulating air for controlling the temperature of said condensing surface.

12. Apparatus as claimed in claim 10, in which said condensing surface comprises a metallic tip plated with platinum black mounted in a transparent conduit, so as to permit a beam ofli ht to strike the surface of the tip for indicating condensation of liquid thereon.

13. Ap aratus as claimed in claim 10, in which sald condensing surface comprises a metallic tip plated with platinum black mounted upon and closing the end of a tube through which air is adapted to be passed for cooling said tip.

14. Apparatus as claimed in claim 10, in which said condensing surface comprises a metallic surface plated with platinum black, the temperature of which' is adapted to be determined by a thermo-couple in contact with said surface.

15. Apparatus for determining the equilibrium vaporization end-point of iquids, comprising means for the equilibrium vaporizaliquid, means for superheating the vapors generated, a platinum-black surface over which the superheated vapors are adapted to pass, means for reducing the temperatlue of said platinum-black surface during the'passage of superheated vapors thereover, and means for ascertaining the temperature of said surface. I

16. Apparatus as claimed in claim 15, in which said vaporization and superheating means are steam-jacketed and means is provided for passing steam therethrough and for ascertaining the heating effect of the steam in said jacket.

17. Apparatus as claimed in claim 15. in

which means is provided for varying the temperature for effecting equilibrium vaporization and the superheating of said vapors.

18. Apparatus for determining the equilibriuin vaporization end-point of liquids, comprising a conduit, means in said conduit for surfacing liquid transversely of the conduit and the direction of flow therethrough, means for heating said conduit for vaporlz ing said liquid surfaces in the presence of the vapors generated, thereby facilitating equilibrium vaporization, means for superheating said vapors upon completion of vaporization, a metallic tip covered with platinum black, means for conductinmthe superheated vapors over said platinum black tip, means for circulating air against said tip for cooling the same, and means associated with said tip for ascertaining the temperature thereof.

19. Apparatus as claimed in claim 18, in which said platinum black tip is mounted in a conduit passing through a Dewar bulb and the means for ascertaining the temperature of said tip comprises a thermocouple adapted to be connected with a pyrometer.

20. Apparatus for determining the equilibrium end point of vaporization or the dew point of liquids or mixtures of consolute liquids, comprising means for the complete vaporization of the liquids, means for superheating the resulting vapors, a metallic surface rendered dead black by a coating of finely divided material for indicatin condensation of a portion of the super eated vapors which are passed thereover and means for ascertaining the temperature of said surface.

CHARLES E. PARSONS. RESTON STEVENSON.

lit) 

